WO2018106429A1 - Enhanced handover mechanism - Google Patents

Abstract

Systems and methods of handover are disclosed. The UE initiates an autonomous handover timer based on triggering of a measurement report. The autonomous handover timer is dependent on the UE mobility and unlicensed spectrum channel occupancy used by the UE. The UE selects autonomous handover or network-based handover dependent on whether a handover command and autonomous handover information have been received prior to expiration of the timer. The UE performs network-controlled handover when the handover command is received prior to expiration of the timer and autonomous handover otherwise. The UE performs contention-based RACH handover to a target eNB indicated by a target eNB ID in the autonomous handover information or based on the measurement report when the autonomous handover information is not received.

Description

ENHANCED HANDOVER MECHANISM PRIORITY CLAIM

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No.62/431,298, filed December 7, 2016, entitled “ENHANCED HANDOVER MECHANISM,” and U.S. Provisional Patent Application Serial No.62/433,653, filed December 13, 2016, entitled “ENHANCED HANDOVER MECHANISM,” each of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments pertain to radio access networks. Some embodiments relate to handover in cellular and wireless local area network (WLAN) networks, including Third Generation Partnership Project Long Term Evolution (3GPP LTE) networks and LTE advanced (LTE-A) networks as well as 4^th generation (4G) networks and 5^th generation (5G) networks. BACKGROUND

[0003] The use of 3GPP LTE systems (including both LTE and LTE-A systems) has increased due to both an increase in the types of devices user equipment (UEs) using network resources as well as the amount of data and bandwidth being used by various applications, such as video streaming, operating on these UEs. LTE networks typically operate in a number of radio frequency (RF) bands licensed to a wireless operator in which base stations (evolved node Bs (eNBs)) and an increasing number and varying type of user equipment (UE) communicate.

[0004] Mobile connectivity is continually important is modern life. To this end, one goal that networks strive for is to provide sufficient signal strength from the radio access network (RAN). Especially in cases in which the UE is moving rapidly or the density of eNBs is high, this may involve multiple handovers between eNBs within the RAN. Each handover involves a variety of control signals between the UE and the RAN and between the RAN and the evolved packet core (EPC). In particular, data destined for the source eNB is stored in the EPC during the process of handover and eventually rerouted to the new source eNB. In some environments, however, handover communications between the UE and RAN may be lost, resulting in lost data. BRIEF DESCRIPTION OF THE FIGURES

[0005] In the figures, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The figures illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0006] FIG.1 illustrates an architecture of a system of a network in accordance with some embodiments.

[0007] FIG.2 illustrates example components of a device in accordance with some embodiments.

[0008] FIG.3 illustrates example interfaces of baseband circuitry in accordance with some embodiments.

[0009] FIG.4 is an illustration of a control plane protocol stack in accordance with some embodiments.

[0010] FIG.5 is an illustration of a user plane protocol stack in accordance with some embodiments.

[0011] FIG.6 is a block diagram illustrating components, according to some example embodiments, able to read instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein.

[0012] FIG.7 illustrates a handover process in accordance with some embodiments.

[0013] FIG.8 illustrates a handover process in accordance with some embodiments. DETAILED DESCRIPTION

[0014] The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0015] FIG.1 illustrates an architecture of a system 100 of a network in accordance with some embodiments. The system 100 is shown to include a user equipment (UE) 101 and a UE 102. The UEs 101 and 102 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non- mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface.

[0016] In some embodiments, any of the UEs 101 and 102 can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), Proximity-Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived connections. The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network.

[0017] The UEs 101 and 102 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN) 110 - the RAN 110 may be, for example, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), a NextGen RAN (NG RAN), or some other type of RAN. The UEs 101 and 102 utilize connections 103 and 104, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections 103 and 104 are illustrated as an air interface to enable

communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code-division multiple access (CDMA) network protocol, a Push-to- Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a 5G protocol, a New Radio (NR) protocol, and the like.

[0018] In this embodiment, the UEs 101 and 102 may further directly exchange communication data via a ProSe interface 105. The ProSe interface 105 may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

[0019] The UE 102 is shown to be configured to access an access point (AP) 106 via connection 107. The connection 107 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 106 would comprise a wireless fidelity (WiFi®) router. In this example, the AP 106 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).

[0020] The RAN 110 can include one or more access nodes that enable the connections 103 and 104. These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gigabit NodeBs - gNBs), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The RAN 110 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 111, and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node 112.

[0021] Any of the RAN nodes 111 and 112 can terminate the air interface protocol and can be the first point of contact for the UEs 101 and 102. In some embodiments, any of the RAN nodes 111 and 112 can fulfill various logical functions for the RAN 110 including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.

[0022] In accordance with some embodiments, the UEs 101 and 102 can be configured to communicate using Orthogonal Frequency-Division

Multiplexing (OFDM) communication signals with each other or with any of the RAN nodes 111 and 112 over a multicarrier communication channel in accordance various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers.

[0023] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 111 and 112 to the UEs 101 and 102, while uplink transmissions can utilize similar techniques. The grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time- frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated. There are several different physical downlink channels that are conveyed using such resource blocks.

[0024] The physical downlink shared channel (PDSCH) may carry user data and higher-layer signaling to the UEs 101 and 102. The physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs 101 and 102 about the transport format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) information related to the uplink shared channel. Typically, downlink scheduling (assigning control and shared channel resource blocks to the UE 102 within a cell) may be performed at any of the RAN nodes 111 and 112 based on channel quality information fed back from any of the UEs 101 and 102. The downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs 101 and 102.

[0025] The PDCCH may use control channel elements (CCEs) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub-block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs). Four Quadrature Phase Shift Keying (QPSK) symbols may be mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DCI) and the channel condition. There can be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L=1, 2, 4, or 8).

[0026] Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts. For example, some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission. The EPDCCH may be transmitted using one or more enhanced the control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations.

[0027] The RAN 110 is shown to be communicatively coupled to a core network (CN) 120—via an S1 interface 113. In embodiments, the CN 120 may be an evolved packet core (EPC) network, a NextGen Packet Core (NPC) network, or some other type of CN. In this embodiment, the S1 interface 113 is split into two parts: the S1-U interface 114, which carries traffic data between the RAN nodes 111 and 112 and the serving gateway (S-GW) 122, and the S1- mobility management entity (MME) interface 115, which is a signaling interface between the RAN nodes 111 and 112 and MMEs 121.

[0028] In this embodiment, the CN 120 comprises the MMEs 121, the S- GW 122, the Packet Data Network (PDN) Gateway (P-GW) 123, and a home subscriber server (HSS) 124. The MMEs 121 may be similar in function to the control plane of legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN). The MMEs 121 may manage mobility aspects in access such as gateway selection and tracking area list management. The HSS 124 may comprise a database for network users, including subscription-related information to support the network entities’ handling of communication sessions. The CN 120 may comprise one or several HSSs 124, depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc. For example, the HSS 124 can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc.

[0029] The S-GW 122 may terminate the S1 interface 113 towards the RAN 110, and routes data packets between the RAN 110 and the CN 120. In addition, the S-GW 122 may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. [0030] The P-GW 123 may terminate an SGi interface toward a PDN. The P-GW 123 may route data packets between the EPC network 123 and external networks such as a network including the application server 130 (alternatively referred to as application function (AF)) via an Internet Protocol (IP) interface 125. Generally, the application server 130 may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). In this embodiment, the P-GW 123 is shown to be communicatively coupled to an application server 130 via an IP communications interface 125. The application server 130 can also be configured to support one or more communication services (e.g., Voice-over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs 101 and 102 via the CN 120.

[0031] The P-GW 123 may further be a node for policy enforcement and charging data collection. Policy and Charging Enforcement Function (PCRF) 126 is the policy and charging control element of the CN 120. In a non-roaming scenario, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE’s Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with local breakout of traffic, there may be two PCRFs associated with a UE’s IP-CAN session: a Home PCRF (H-PCRF) within a HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF 126 may be

communicatively coupled to the application server 130 via the P-GW 123. The application server 130 may signal the PCRF 126 to indicate a new service flow and select the appropriate Quality of Service (QoS) and charging parameters. The PCRF 126 may provision this rule into a Policy and Charging Enforcement Function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server 130.

[0032] FIG.2 illustrates example components of a device 200 in accordance with some embodiments. In some embodiments, the device 200 may include application circuitry 202, baseband circuitry 204, Radio Frequency (RF) circuitry 206, front-end module (FEM) circuitry 208, one or more antennas 210, and power management circuitry (PMC) 212 coupled together at least as shown. The components of the illustrated device 200 may be included in a UE or a RAN node. In some embodiments, the device 200 may include less elements (e.g., a RAN node may not utilize application circuitry 202, and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device 200 may include additional elements such as, for example, memory/storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C-RAN) implementations).

[0033] The application circuitry 202 may include one or more application processors. For example, the application circuitry 202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors,

application processors, etc.). The processors may be coupled with or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications or operating systems to run on the device 200. In some embodiments, processors of application circuitry 202 may process IP data packets received from an EPC.

[0034] The baseband circuitry 204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 204 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 206 and to generate baseband signals for a transmit signal path of the RF circuitry 206. Baseband processing circuity 204 may interface with the application circuitry 202 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 206. For example, in some embodiments, the baseband circuitry 204 may include a third generation (3G) baseband processor 204A, a fourth generation (4G) baseband processor 204B, a 5G baseband processor 204C, or other baseband processor(s) 204D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 204 (e.g., one or more of baseband processors 204A-D) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 206. In other embodiments, some or all of the functionality of baseband processors 204A-D may be included in modules stored in the memory 204G and executed via a Central Processing Unit (CPU) 204E. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 204 may include Fast-Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 204 may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC)

encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[0035] In some embodiments, the baseband circuitry 204 may include one or more audio digital signal processor(s) (DSP) 204F. The audio DSP(s) 204F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 204 and the application circuitry 202 may be implemented together such as, for example, on a system on a chip (SOC).

[0036] In some embodiments, the baseband circuitry 204 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 204 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 204 is configured to support radio communications of more than one wireless protocol may be referred to as multi- mode baseband circuitry.

[0037] RF circuitry 206 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 206 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 206 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 208 and provide baseband signals to the baseband circuitry 204. RF circuitry 206 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 204 and provide RF output signals to the FEM circuitry 208 for transmission.

[0038] In some embodiments, the receive signal path of the RF circuitry 206 may include mixer circuitry 206A, amplifier circuitry 206B and filter circuitry 206C. In some embodiments, the transmit signal path of the RF circuitry 206 may include filter circuitry 206C and mixer circuitry 206A. RF circuitry 206 may also include synthesizer circuitry 206D for synthesizing a frequency for use by the mixer circuitry 206A of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 206A of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 208 based on the synthesized frequency provided by synthesizer circuitry 206D. The amplifier circuitry 206B may be configured to amplify the down-converted signals and the filter circuitry 206C may be a low- pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 204 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 206A of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect. [0039] In some embodiments, the mixer circuitry 206A of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 206D to generate RF output signals for the FEM circuitry 208. The baseband signals may be provided by the baseband circuitry 204 and may be filtered by filter circuitry 206C.

[0040] In some embodiments, the mixer circuitry 206A of the receive signal path and the mixer circuitry 206A of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry 206A of the receive signal path and the mixer circuitry 206A of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 206A of the receive signal path and the mixer circuitry 206A may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry 206A of the receive signal path and the mixer circuitry 206A of the transmit signal path may be configured for super-heterodyne operation.

[0041] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 204 may include a digital baseband interface to communicate with the RF circuitry 206.

[0042] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[0043] In some embodiments, the synthesizer circuitry 206D may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 206D may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[0044] The synthesizer circuitry 206D may be configured to synthesize an output frequency for use by the mixer circuitry 206A of the RF circuitry 206 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 206D may be a fractional N/N+1 synthesizer.

[0045] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 204 or the applications processor 202 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look- up table based on a channel indicated by the applications processor 202.

[0046] Synthesizer circuitry 206D of the RF circuitry 206 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+1 (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0047] In some embodiments, synthesizer circuitry 206D may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 206 may include an IQ/polar converter.

[0048] FEM circuitry 208 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 210, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 206 for further processing. FEM circuitry 208 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 206 for transmission by one or more of the one or more antennas 210. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 206, solely in the FEM 208, or in both the RF circuitry 206 and the FEM 208.

[0049] In some embodiments, the FEM circuitry 208 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 206). The transmit signal path of the FEM circuitry 208 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 206), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 210).

[0050] In some embodiments, the PMC 212 may manage power provided to the baseband circuitry 204. In particular, the PMC 212 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC 212 may often be included when the device 200 is capable of being powered by a battery, for example, when the device is included in a UE. The PMC 212 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics.

[0051] While FIG.2 shows the PMC 212 coupled only with the baseband circuitry 204. However, in other embodiments, the PMC 212 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 202, RF circuitry 206, or FEM 208.

[0052] In some embodiments, the PMC 212 may control, or otherwise be part of, various power saving mechanisms of the device 200. For example, if the device 200 is in an RRC_Connected state, where it is still connected to the RAN node as it expects to receive traffic shortly, then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the device 200 may power down for brief intervals of time and thus save power.

[0053] If there is no data traffic activity for an extended period of time, then the device 200 may transition to an RRC_Idle state. In the RRC_Idle state, the device 200 may disconnect from the network and avoid performing operations such as channel quality feedback, handover, etc. The device 200 may enter a very low power state and perform paging in which the device 200 may periodically wake up to listen to the network and then power down again. To receive data, the device 200 may transition back to the RRC_Connected state.

[0054] An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to the network and may power down completely. Any data sent during this time incurs a large delay and it is assumed the delay is acceptable.

[0055] Processors of the application circuitry 202 and processors of the baseband circuitry 204 may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry 204, alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 204 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below.

[0056] FIG.3 illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry 204 of FIG.2 may comprise processors 204A-XT04E and a memory 204G utilized by said processors. Each of the processors 204A-XT04E may include a memory interface, 304A-XU04E, respectively, to send/receive data to/from the memory 204G.

[0057] The baseband circuitry 204 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 312 (e.g., an interface to send/receive data to/from memory external to the baseband circuitry 204), an application circuitry interface 314 (e.g., an interface to send/receive data to/from the application circuitry 202 of FIG.2), an RF circuitry interface 316 (e.g., an interface to send/receive data to/from RF circuitry 206 of FIG.2), a wireless hardware connectivity interface 318 (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface 320 (e.g., an interface to send/receive power or control signals to/from the PMC 212).

[0058] FIG.4 is an illustration of a control plane protocol stack in accordance with some embodiments. In this embodiment, a control plane 400 is shown as a communications protocol stack between the UE 101 (or alternatively, the UE 102), the RAN node 111 (or alternatively, the RAN node 112), and the MME 121.

[0059] The PHY layer 401 may transmit or receive information used by the MAC layer 402 over one or more air interfaces. The PHY layer 401 may further perform link adaptation or adaptive modulation and coding (AMC), power control, cell search (e.g., for initial synchronization and handover purposes), and other measurements used by higher layers, such as the RRC layer 405. The PHY layer 401 may still further perform error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, modulation/demodulation of physical channels, interleaving, rate matching, mapping onto physical channels, and Multiple Input Multiple Output (MIMO) antenna processing.

[0060] The MAC layer 402 may perform mapping between logical channels and transport channels, multiplexing of MAC service data units (SDUs) from one or more logical channels onto transport blocks (TB) to be delivered to PHY via transport channels, de-multiplexing MAC SDUs to one or more logical channels from transport blocks (TB) delivered from the PHY via transport channels, multiplexing MAC SDUs onto TBs, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), and logical channel prioritization.

[0061] The RLC layer 403 may operate in a plurality of modes of operation, including: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The RLC layer 403 may execute transfer of upper layer protocol data units (PDUs), error correction through automatic repeat request (ARQ) for AM data transfers, and concatenation, segmentation and reassembly of RLC SDUs for UM and AM data transfers. The RLC layer 403 may also execute re-segmentation of RLC data PDUs for AM data transfers, reorder RLC data PDUs for UM and AM data transfers, detect duplicate data for UM and AM data transfers, discard RLC SDUs for UM and AM data transfers, detect protocol errors for AM data transfers, and perform RLC re-establishment.

[0062] The PDCP layer 404 may execute header compression and decompression of IP data, maintain PDCP Sequence Numbers (SNs), perform in-sequence delivery of upper layer PDUs at re-establishment of lower layers, eliminate duplicates of lower layer SDUs at re-establishment of lower layers for radio bearers mapped on RLC AM, cipher and decipher control plane data, perform integrity protection and integrity verification of control plane data, control timer-based discard of data, and perform security operations (e.g., ciphering, deciphering, integrity protection, integrity verification, etc.).

[0063] The main services and functions of the RRC layer 405 may include broadcast of system information (e.g., included in Master Information Blocks (MIBs) or System Information Blocks (SIBs) related to the non-access stratum (NAS)), broadcast of system information related to the access stratum (AS), paging, establishment, maintenance and release of an RRC connection between the UE and E-UTRAN (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), establishment, configuration, maintenance and release of point to point Radio Bearers, security functions including key management, inter radio access technology (RAT) mobility, and measurement configuration for UE

measurement reporting. The MIBs and SIBs may comprise one or more information elements (IEs), which may each comprise individual data fields or data structures.

[0064] The UE 101 and the RAN node 111 may utilize a Uu interface (e.g., an LTE-Uu interface) to exchange control plane data via a protocol stack comprising the PHY layer 401, the MAC layer 402, the RLC layer 403, the PDCP layer 404, and the RRC layer 405.

[0065] The non-access stratum (NAS) protocols 406 form the highest stratum of the control plane between the UE 101 and the MME 121. The NAS protocols 406 support the mobility of the UE 101 and the session management procedures to establish and maintain IP connectivity between the UE 101 and the P-GW 123.

[0066] The S1 Application Protocol (S1-AP) layer 415 may support the functions of the S1 interface and comprise Elementary Procedures (EPs). An EP is a unit of interaction between the RAN node 111 and the CN 120. The S1-AP layer services may comprise two groups: UE-associated services and non UE- associated services. These services perform functions including, but not limited to: E-UTRAN Radio Access Bearer (E-RAB) management, UE capability indication, mobility, NAS signaling transport, RAN Information Management (RIM), and configuration transfer.

[0067] The Stream Control Transmission Protocol (SCTP) layer (alternatively referred to as the SCTP/IP layer) 414 may ensure reliable delivery of signaling messages between the RAN node 111 and the MME 121 based, in part, on the IP protocol, supported by the IP layer 413. The L2 layer 412 and the L1 layer 411 may refer to communication links (e.g., wired or wireless) used by the RAN node and the MME to exchange information.

[0068] The RAN node 111 and the MME 121 may utilize an S1-MME interface to exchange control plane data via a protocol stack comprising the L1 layer 411, the L2 layer 412, the IP layer 413, the SCTP layer 414, and the S1-AP layer 415.

[0069] FIG.5 is an illustration of a user plane protocol stack in accordance with some embodiments. In this embodiment, a user plane 500 is shown as a communications protocol stack between the UE 101 (or alternatively, the UE 102), the RAN node 111 (or alternatively, the RAN node 112), the S-GW 122, and the P-GW 123. The user plane 500 may utilize at least some of the same protocol layers as the control plane 400. For example, the UE 101 and the RAN node 111 may utilize a Uu interface (e.g., an LTE-Uu interface) to exchange user plane data via a protocol stack comprising the PHY layer 401, the MAC layer 402, the RLC layer 403, the PDCP layer 404.

[0070] The General Packet Radio Service (GPRS) Tunneling Protocol for the user plane (GTP-U) layer 504 may be used for carrying user data within the GPRS core network and between the radio access network and the core network. The user data transported can be packets in any of IPv4, IPv6, or PPP formats, for example. The UDP and IP security (UDP/IP) layer 503 may provide checksums for data integrity, port numbers for addressing different functions at the source and destination, and encryption and authentication on the selected data flows. The RAN node 111 and the S-GW 122 may utilize an S1-U interface to exchange user plane data via a protocol stack comprising the L1 layer 411, the L2 layer 412, the UDP/IP layer 503, and the GTP-U layer 504. The S-GW 122 and the P-GW 123 may utilize an S5/S8a interface to exchange user plane data via a protocol stack comprising the L1 layer 411, the L2 layer 412, the UDP/IP layer 503, and the GTP-U layer 504. As discussed above with respect to FIG.4, NAS protocols support the mobility of the UE 101 and the session management procedures to establish and maintain IP connectivity between the UE 101 and the P-GW 123. [0071] FIG.6 is a block diagram illustrating components, according to some example embodiments, able to read instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically, FIG.6 shows a diagrammatic representation of hardware resources 600 including one or more processors (or processor cores) 610, one or more memory/storage devices 620, and one or more communication resources 630, each of which may be communicatively coupled via a bus 640. For

embodiments where node virtualization (e.g., NFV) is utilized, a hypervisor 602 may be executed to provide an execution environment for one or more network slices/sub-slices to utilize the hardware resources 600

[0072] The processors 610 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) such as a baseband processor, an application specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor 612 and a processor 614.

[0073] The memory/storage devices 620 may include main memory, disk storage, or any suitable combination thereof. The memory/storage devices 620 may include, but are not limited to any type of volatile or non-volatile memory such as dynamic random access memory (DRAM), static random-access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), Flash memory, solid-state storage, etc.

[0074] The communication resources 630 may include interconnection or network interface components or other suitable devices to communicate with one or more peripheral devices 604 or one or more databases 606 via a network 608. For example, the communication resources 630 may include wired communication components (e.g., for coupling via a Universal Serial Bus (USB)), cellular communication components, NFC components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components.

[0075] Instructions 650 may comprise software, a program, an application, an applet, an app, or other executable code for causing at least any of the processors 610 to perform any one or more of the methodologies discussed herein. The instructions 650 may reside, completely or partially, within at least one of the processors 610 (e.g., within the processor’s cache memory), the memory/storage devices 620, or any suitable combination thereof. In some embodiments, the instructions 650 may reside on a tangible, non- volatile communication device readable medium, which may include a single medium or multiple media. Furthermore, any portion of the instructions 650 may be transferred to the hardware resources 600 from any combination of the peripheral devices 604 or the databases 606. Accordingly, the memory of processors 610, the memory/storage devices 620, the peripheral devices 604, and the databases 606 are examples of computer-readable and machine-readable media.

[0076] As above, high mobility or dense environments with large numbers of (micro and other) eNBs may increase the frequency of a UE engaging in the handover process. FIG.7 illustrates a handover process 700 in accordance with some embodiments. The various components shown in FIG.7 may be described in relation to FIGS.1-6. Some of the processes that occur during handover may not be shown for convenience.

[0077] The handover may be an inter- or intra-network E-UTRAN handover. Independent of whether the handover is intra- or inter-network, the handover process may take a number of operations and it may overall take a significant amount of time to complete the operations involved in the handover process. These operations may include, for example, a UE 710 in RRC

Connected mode measuring signal and/or channel qualities of reference signals transmitted by a source eNB 720 to which the UE 710 is attached. The measurements may include, for example, signal-to-noise ratio measurements (SINR) signal-to-interference ratio measurements (SIR), or error rate, among others. The UE 710 may subsequently transmit a measurement report to the source eNB 720.

[0078] The source eNB 720 may determine from the measurement report whether to initiate handover. If handover is to occur, the source eNB 720 may determine, e.g., based on the UE direction of travel, a target eNB 730 to which to handover the UE. The source eNB 720 may then send a handover request containing UE information to the target eNB 730.

[0079] The target eNB 730 may engage in admission control after receiving the handover request. Admission control may involve, among others, the target eNB 730 determining whether to accept the UE 710, e.g., based on loading of the target eNB 730, and perhaps one or more neighboring cells. After acceptance of the handover request of the UE 710, the target eNB 730 may transmit to the source eNB 720 a handover request acknowledgement (ACK).

[0080] The source eNB 720 may, in response to reception of the handover request acknowledgement ACK, then send allocation and

reconfiguration information to the UE 710 and instruct the UE 710 to perform handover to the target eNB 730 via a handover command. The reconfiguration information may be sent in a RRCConnectionReconfiguration message that includes the handover command. The RRCConnectionReconfiguration message may include, for example, the mobilityControlInformation information element (IE), and the new Cell Radio Network Temporary Identifier (C-RNTI) of the target eNB 730.

[0081] The source eNB 720 may send a SN Status Transfer message to the target eNB 730. The SN Status Transfer message may convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of radio access bearers associated with the UE 710 for which PDCP status preservation applies.

[0082] After reception of the RRCConnectionReconfiguration message, the UE 710 may subsequently detach from the source eNB 720 and attach to the target eNB 730. The UE 710 may thus synchronize to and access the target eNB 730 using a random access channel (RACH) process after obtaining timing information from the target eNB 730. The UE 710 may transmit a RRCConnectionReconfigurationComplete message containing the new C-RNTI to the target eNB 730 when synchronization with the target eNB 730 is complete.

[0083] The target eNB 730 may begin sending data to the UE 710. In particular, once the target eNB 730 determines that the UE is able to communicate, the target eNB 730 may transmit a path switch message to the MME 750 to indicate that the eNB serving the UE 710 has changed. The MME 750 may, in response, send a user plane update request to the S-GW 740 to update the user plane. The S-GW 740 may use the user plane update request to switch the downlink path from the source eNB 720 to the target eNB 730.

[0084] The S-GW 740 may also send one or more end marker packets to the source eNB 720 before releasing the user plane resources of the UE 710 and before sending a response to the update request to the MME 750. The source eNB 720 may supply the end marker to the target UE. The MME 750 may subsequently confirm the update to the target eNB 730 in a path switch ACK message in response to the path switch message. The target eNB 730 then may confirm this information with the source eNB 720 through a UE context release message. The source eNB 720 may then release user and control plane related resources associated to the UE context.

[0085] Thus, identification, address, channel, signal strength, security, Quality of Service (QoS) and other information may be communicated from the UE to the source and/or target eNB 730 to enable the target eNB 730 to select the appropriate channel to use in communications with the UE. After the information is communicated, a communication link between the UE and target eNB 730 may be established and subsequently, the existing communication link between the UE and the source eNB 720 may be torn down.

[0086] As shown in FIG.7, there are a number of communications between the UE and the RAN during the handover process. In environments in which there is a significant amount of interference, or the signal strength is low (e.g., at the cell edge of the serving cell), handover and/or radio link failure (RLF) may occur. The majority of handover and radio link failures may be due to the inability of the UE to receive the handover-related control messages, such as the handover command or the RRCConnectionReconfiguration message sent by source eNB. In some embodiments, such as MulteFire in which only carriers in the unlicensed spectrum are used, there is even a higher chance of missing the handover-related command messages due to the protocol for using the unlicensed band (or spectrum). In particular, the use of Listen Before Talk (LBT) in the unlicensed spectrum may result in handover-related command messages not being received as in LBT, sensing of the channel may be performed to make sure that the channel is clear, and only after sensing a clear channel is an OTA communication transmitted. This may result in data being lost in communications between the UE and RAN.

[0087] To mitigate these issues and provide for successful handover even when some of the handover control messages are lost, a timer may be provided to, upon expiry of the timer, allow the UE to handover to a neighboring cell using an autonomous procedure based on the current knowledge of the UE about the neighboring cell. As explained in more detail below, when the UE misses the handover command from the eNB, and downlink conditions continue to deteriorate, the UE may start a RLF procedure. This procedure may include initiation of a RLF timer T310 (nominally 1 sec) when the UE receives N310 consecutive out-of-sync frames. When T310 expires, the UE may initiate a different timer T311 (nominally 1 sec) and initiate the RRC reestablishment procedure. In some circumstances, the UE may be unable to establish connection with a target eNB before the T311 timer expires. This may lead to the UE undertaking a series of procedures, including dropping back from the RRC Connected mode to the RRC idle mode, selecting a new target eNB, acquiring system information of the new target eNB, transmitting a contention- based RACH procedure, and then re-establishing connection with the new target eNB.

[0088] FIG.8 illustrates a handover process 800 in accordance with some embodiments. The various components shown in FIG.8 may be described in relation to FIGS.1-6. Some of the processes that occur during handover may not be shown for convenience, including some of the processes shown in FIG.7 (e.g., communications between the UE/RAN and the EPC and within the EPC). In some embodiments, some of the handover communications may be based on those provided in the MulteFire 1.0 specification. As above, the transmitting entity (e.g., UE or eNB) may encode specific information for transmission through the appropriate interface and the receiving entity (e.g., eNB or UE) may decode the information received through the interface.

[0089] As before, the handover 800 shown in FIG.8 may be an inter- or intra-network E-UTRAN handover. The operations may include, for example, a UE 810 in RRC Connected mode measuring the above qualities of reference signals transmitted by a source eNB 820 to which the UE 810 is attached. The measurements may be taken at predetermined times.

[0090] The UE 810 may subsequently prepare a measurement report for transmission to the source eNB 820. In addition, the UE 810 may initiate an autonomous handover timer (T380) in response to the measurement report event being triggered. In some embodiments, the autonomous handover timer may be used when a predetermined spectrum condition is met. The predetermined spectrum condition may be that carrier aggregation is used in which carriers in the licensed and unlicensed band are used, or in which only carriers in the unlicensed spectrum are used (MulteFire). The timer length (or time period of the timer) may be configured by the source eNB 820 in higher layer signaling (e.g., an RRC message) or via other UE-specific signaling, e.g., in the DCI of a PDCCH or ePDCCH. The timer length may vary periodically and may be based on mobility of the UE and/or channel occupancy of a channel used by the UE to communicate with the source eNB. The UE mobility may be extrapolated through GPS or other location measurements over a predetermined amount of time and may be instantaneous (over the most recent period) or averaged over a predetermined number of periods. In some embodiments, the timer length may be based on an average mobility of all (or most) UEs in the cell attached to the source eNB 820, in which case the timer length may be provided in a system- wide transmission, such as system information.

[0091] Independent of whether the UE mobility of the UE 810 is used or whether an average UE mobility of multiple UEs is used, the length of the autonomous handover timer may vary similarly. For example, the timer length may vary inversely with UE mobility to avoid radio condition issues with serving cell. On the other hand, the timer length may vary directly with channel occupancy (independent of the UE mobility) to allow the UE to avoid frequent handover and cause increased contention in the RACH procedure. The timer length may thus be a function of the UE mobility and channel occupancy.

[0092] The UE 810 may subsequently transmit the measurement report to the source eNB 820. Transmission of the measurement report may occur on the unlicensed band and use LBT. In some embodiments, the measurement report may include a timestamp of when the autonomous handover timer is initiated. This may permit the source eNB 820 to avoid transmission of the handover command if the source eNB 820 determines that the autonomous handover timer has expired, thereby conserving network resources.

[0093] The source eNB 820 may determine from the measurement report whether to initiate handover. The determination may depend on eNB implementation. If handover is to occur, the source eNB 820 may determine, e.g., based on the UE direction of travel as well as eNB load and UE and eNB priority information, a target eNB 830 to which to handover the UE. The source eNB 820 may then send a handover request containing UE information to the target eNB 830.

[0094] The source eNB 820 may also, after a determination that handover is to occur to the target eNB 830, transmit UE autonomous handover information to the UE 810. Transmission of the autonomous handover information may occur on the unlicensed band and use LBT. The UE autonomous handover information may include a list of one or more target eNB IDs to which the UE may attempt attachment and a C-RNTI of the target eNB 830. The list of target eNB IDs may further include prioritization among the target eNBs. The list of target eNB IDs may include fewer than all of the neighboring cells of the source eNB 820. In some embodiments, the UE autonomous handover information may be broadcast or sent via UE-specific control signaling at predetermined times that are unrelated to the handover determination. Thus, the UE autonomous handover information may be sent, for example, prior to triggering of the measurement report or before the handover decision by the source eNB 820. In some embodiments, time period of the autonomous handover timer may be provided in the UE autonomous handover information, and indicated by a flag in the UE autonomous handover information.

[0095] The target eNB 830 may engage in admission control after receiving the handover request. Admission control may involve, as above, the target eNB 830 determining whether to accept the UE 810, e.g., based on loading of the target eNB 830, and perhaps that of one or more neighboring cells, as well as UE priority and perhaps other factors. After acceptance of the handover request of the UE 810, the target eNB 830 may transmit to the source eNB 820 a handover request ACK. The above UE autonomous handover information may be transmitted within the interval after reception of the measurement report from the UE 810 and prior to reception of a handover request ACK from the target eNB 830.

[0096] The source eNB 820 may, in response to reception of the handover request acknowledgement ACK, then send allocation and

reconfiguration information to the UE 810 and instruct the UE 810 to perform handover to the target eNB 830 via a handover command. Transmission of the handover command may occur on the unlicensed band and use LBT. The handover command may be sent in a RRCConnectionReconfiguration message that includes the handover command. The RRCConnectionReconfiguration message may include, for example, the mobilityControlInformation information element (IE), and the new Cell Radio Network Temporary Identifier (C-RNTI) of the target eNB 830.

[0097] In some cases, the UE 810 may receive the handover command before the UE autonomous handover timer expires. The autonomous handover timer may be reset when the handover command is received. In this case, the UE 810 may follow the handover command to perform network-controlled handover to the target eNB 830. The network-controlled handover process can be a 2-element contention-free handover process, or a RACH-less handover. This process may include assignment to the UE 810 of a RACH preamble by the source eNB 820, transmission by the UE 810 of the RACH preamble, RA-RNTI and indication of message size to the target eNB 830, and transmission by the target eNB 830 to the UE 810 of the RA response (e.g., timing advance, temporary C-RNTI, UL grant).

[0098] In other cases, however, the UE 810 may fail to receive the handover command before the UE autonomous handover timer expires. This delay may be due to the LBT process, for example. In this case, whether the UE 810 received the UE autonomous handover information may determine the course of action taken. For example, if the UE 810 received the UE autonomous handover information, the UE 810 may perform autonomous handover based on the list of target eNB IDs. The UE 810 may select among the target eNBs based on prioritization as indicated in the UE autonomous handover information or, if prioritization is not present, randomly among the target eNBs. The UE 810 may start a 4-element contention-based RACH procedure with one of the target eNB. This process may transmission by the UE 810 of a random RACH preamble to the target eNB 830, transmission by the target eNB 830 to the UE 810 of the RA response, transmission by the UE 810 of an ID to the target eNB 830 (e.g., temporary C-RNTI, IMSI, TMSI) and contention resolution by the target eNB 830. In another embodiment, the UE 810 may start a 2-element contention- based RACH procedure.

[0099] If, on the other hand, the UE 810 did not receive the UE autonomous handover information, the UE 810 may then perform autonomous handover to a target eNB based on the measurement report. This handover can be based on the neighbor cell that triggers the measurement event for handover; the measurement event for handover can be, for example: LTE measurement report triggering event A3, in which the neighbor cell quality is better than the serving cell (source eNB 820) by a predetermined offset, or LTE measurement report triggering event A5, in which the neighbor cell quality is better than a first predetermined threshold while the serving cell quality is below a second predetermined threshold. The first and second thresholds may be different and may be independently set. The autonomous handover procedure can be a 2- or 4-element contention-based RACH procedure with the target eNB 830. [00100] In another embodiment, the UE 810 may be provided with an event and/or the UE autonomous handover criteria for the UE autonomous handover. If the UE 810 is provided with the event, the network may indicate an measurement event configuration in system-wide or UE-specific control information. The measurement event configuration may indicate which events can be used for the UE autonomous handover. Alternatively or in addition, the measurement event configuration may indicate a completely new measurement event that can be used for the UE autonomous handover decision by the UE 810. In embodiments in which the UE 810 is provided with the UE autonomous criteria, cell reselection type of criteria can be used. In this case, for example, rankings of the serving cell and neighbor cells may be provided, in which case the UE may select the highest ranked neighbor cell.

[00101] The UE 810 may be authenticated in the same manner independent of whether the UE 810 engages in UE autonomous handover. In some embodiments, a RRC Connection Re-establishment procedure may be used to authenticate the UE 810. In this case, the authentication may be based on the shortMAC-I information element (IE) which is generated based on the PCI of the source cell, C-RNTI and target eNB ID (the 16 least significant bits of the MAC-I calculated using the security configuration of the source cell and the re- establishment cell identity).

[00102] As above, a timing transmission that may be broadcast and/or UE-specific signaling (e.g., RRC or MAC signaling) may be used to provide the time length of the autonomous handover timer. Such signaling may additionally provide other explicit indications, such as the measurement event configuration that enables the UE to perform timer based autonomous handover.

[00103] Independent of whether the UE autonomous handover process is used, the UE 810 may transmit a RRCConnectionReconfigurationComplete message to the target eNB 830 when synchronization with the target eNB 830 is complete. As above, the RRCConnectionReconfigurationComplete message may contain the new C-RNTI. [00104] Examples [00105] Example 1 is an apparatus of a user equipment (UE), the apparatus comprising: processing circuitry arranged to: determine whether a measurement report event is triggered; in response to a determination that the measurement report event has been triggered: initiate an autonomous handover timer having a time period; and encode, for transmission to a source NodeB (NB) on an unlicensed band, a measurement report, transmission of the measurement report in accordance with listen before talk (LBT); after transmission of the measurement report, determine a handover process from a plurality of handover processes to perform a handover from the source NB to a target NB, determination of the handover process dependent on whether a handover command has been received on the unlicensed band in accordance with LBT prior to expiration of the autonomous handover timer; and perform the handover process; and a memory to store the time period.

[00106] In Example 2, the subject matter of Example 1 includes, wherein the processing circuitry is further arranged to: decode a timing transmission from the source NB, the timing transmission comprising the time period of the autonomous handover timer.

[00107] In Example 3, the subject matter of Example 2 includes, wherein: the time period of the autonomous handover timer is dependent on mobility of the UE and channel occupancy of a channel used by the UE.

[00108] In Example 4, the subject matter of Example 3 includes, wherein: the time period of the autonomous handover timer is inversely proportional to the mobility of the UE and proportional to the channel occupancy.

[00109] In Example 5, the subject matter of Examples 1–4 includes, wherein the processing circuitry is further arranged to: follow the handover command to perform network-controlled handover from the source NB to the target NB as the handover process when the handover command is received prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C-RNTI) of the target NB. [00110] In Example 6, the subject matter of Example 5 includes, wherein: the network-controlled handover is a contention-free handover or random access channel (RACH)-less handover.

[00111] In Example 7, the subject matter of Examples 1–6 includes, wherein: the handover process is further dependent on whether autonomous handover information has been received from the source NB prior to expiration of the autonomous handover timer and prior to reception of the handover command, and the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer.

[00112] In Example 8, the subject matter of Example 7 includes, wherein the processing circuitry is further arranged to: perform 2- or 4-step contention- based random access channel (RACH) handover procedure as the handover process from the source NB to a cell indicated by one of the target NB IDs when the autonomous handover information is received by the UE.

[00113] In Example 9, the subject matter of Examples 7–8 includes, wherein the processing circuitry is further arranged to: perform, as the handover process, handover to a target NB based on the measurement report when the autonomous handover information is not received prior to expiration of the autonomous handover timer and prior to reception of the handover command.

[00114] In Example 10, the subject matter of Example 9 includes, wherein: the target NB is a neighbor cell that triggered the measurement report, and the neighbor cell is a neighbor of the source NB.

[00115] In Example 11, the subject matter of Examples 7–10 includes, wherein: the handover process comprises autonomous handover, the memory configured to store at least one of an event or autonomous handover criteria to trigger the autonomous handover.

[00116] In Example 12, the subject matter of Example 11 includes, wherein the processing circuitry is further arranged to: decode, from the source NB, a measurement event configuration that indicates at least one event to trigger the autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell.

[00117] In Example 13, the subject matter of Examples 11–12 includes, wherein the processing circuitry is further arranged to: decode, from the source NB, cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell.

[00118] In Example 14, the subject matter of Examples 1–13 includes, wherein: the measurement report comprises a timestamp that indicates a time of initiation of the autonomous handover timer, and whether the handover command is received is dependent on the timestamp.

[00119] In Example 15, the subject matter of Examples 1–14 includes, wherein: carriers used in communication between the UE and the source NB are limited to the unlicensed band such that handover transmissions between the UE and the source NB occur on the unlicensed band.

[00120] In Example 16, the subject matter of Examples 1–15 includes, wherein: at least one of the source or target NB is an evolved NB (eNB).

[00121] In Example 17, the subject matter of Examples 1–16 includes, wherein: at least one of the source or target NB is gigabit NB (gNB).

[00122] In Example 18, the subject matter of Examples 1–17 includes, wherein: the processing circuitry comprises a baseband processor configured to encode transmissions to, and decode transmissions from, the source NB.

[00123] Example 19 is an apparatus of a source NodeB (NB), the apparatus comprising: processing circuitry arranged to: decode, from a user equipment (UE), a measurement report received on an unlicensed band in accordance with listen before talk (LBT), the measurement report comprising a timestamp that indicates a time of initiation by the UE of an autonomous handover timer; determine from the measurement report, whether handover of the UE to a target NB is to occur; and engage in a handover process of a plurality of handover processes in response to a determination that a handover of the UE to a target NB is to occur, the handover process on the unlicensed band in accordance with LBT, the handover process dependent on the autonomous handover timer; and a memory to store the autonomous handover timer. [00124] In Example 20, the subject matter of Example 19 includes, wherein the processing circuitry is further arranged to: encode, for transmission to the UE, a timing transmission, the timing transmission comprising the time period of the autonomous handover timer.

[00125] In Example 21, the subject matter of Example 20 includes, wherein: the time period of the autonomous handover timer is dependent on mobility of the UE and channel occupancy of a channel used by the UE.

[00126] In Example 22, the subject matter of Examples 19–21 includes, wherein: the handover is network-controlled contention-free or random access channel (RACH)-less handover when a handover command is transmitted from the source NB prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C- RNTI) of the target NB.

[00127] In Example 23, the subject matter of Examples 19–22 includes, wherein the processing circuitry is further arranged to: encode, for transmission to the UE, autonomous handover information after reception of the measurement report and prior to expiration of the autonomous handover timer and prior to transmission to the UE of a handover command, and the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer.

[00128] In Example 24, the subject matter of Example 23 includes, wherein: handover to a target NB is based on the measurement report when the autonomous handover information is not received by the UE.

[00129] In Example 25, the subject matter of Examples 23–24 includes, wherein the processing circuitry is further arranged to: encode, for transmission to the UE, at least one of: a measurement event configuration that indicates at least one event to trigger autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell, or cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell. [00130] In Example 26, the subject matter of Examples 19–25 includes, wherein the processing circuitry is further arranged to: in response to a determination to handover the UE to the target NB, determine, based on the timestamp, whether the autonomous handover timer has expired; in response to a determination that the autonomous handover timer has not expired, encode a handover command for transmission to the UE, the handover command configured to instruct the UE to handover to the target NB; and in response to a determination that the autonomous handover timer has expired, avoid transmission of the handover command.

[00131] Example 27 is a computer-readable storage medium that stores instructions for execution by one or more processors of a user equipment (UE), the one or more processors to configure the UE to, when the instructions are executed: initiate an autonomous handover timer based on triggering of a measurement report, a time period of the autonomous handover timer dependent on mobility of the UE and channel occupancy of an unlicensed spectrum channel used by the UE; determine which of autonomous handover or network-based handover from a source NodeB (NB) to a target NB to perform dependent on whether a handover command and autonomous handover information have been received prior to expiration of the autonomous handover timer; and perform the autonomous handover or network-based handover determined.

[00132] In Example 28, the subject matter of Example 27 includes, wherein the instructions further configure the one or more processors to configure the UE to: perform network-controlled handover when the handover command is received prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C- RNTI) of the target NB.

[00133] In Example 29, the subject matter of Examples 27–28 includes, wherein: the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer; and when the handover command is not received prior to expiration of the autonomous handover timer, the instructions further configure the one or more processors to configure the UE to perform a 2- or 4-step contention-based random access channel (RACH) handover to a target NB indicated by one of the target NB IDs when the autonomous handover information is received by the UE and perform handover to the target NB based on the measurement report when the autonomous handover information fails to be received by the UE.

[00134] In Example 30, the subject matter of Example 29 includes, wherein the instructions further configure the one or more processors to configure the UE to: receive, from the source NB, a measurement event configuration that indicates at least one of: at least one event to trigger autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell, or cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell.

[00135] Example 31 is at least one machine-readable medium including instructions that, when executed by processing circuitry, cause the processing circuitry to perform operations to implement of any of Examples 1–30.

[00136] Example 32 is an apparatus comprising means to implement of any of Examples 1–30.

[00137] Example 33 is a system to implement of any of Examples 1–30.

[00138] Example 34 is a method to implement of any of Examples 1–30.

[00139] Although an embodiment has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The

accompanying drawings that form a part hereof show, by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

[00140] The subject matter may be referred to herein, individually and/or collectively, by the term“embodiment” merely for convenience and without intending to voluntarily limit the scope of this application to any single inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.

[00141] In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of "at least one" or "one or more." In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indicated. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, UE, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[00142] The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

What is claimed is: 1. An apparatus of a user equipment (UE), the apparatus comprising: processing circuitry arranged to:

determine whether a measurement report event is triggered; in response to a determination that the measurement report event has been triggered:

initiate an autonomous handover timer having a time period; and

encode, for transmission to a source NodeB (NB) on an unlicensed band, a measurement report, transmission of the measurement report in accordance with listen before talk (LBT); after transmission of the measurement report, determine a handover process from a plurality of handover processes to perform a handover from the source NB to a target NB, determination of the handover process dependent on whether a handover command has been received on the unlicensed band in accordance with LBT prior to expiration of the autonomous handover timer; and

perform the handover process; and

a memory to store the time period.

2. The apparatus of claim 1, wherein the processing circuitry is further arranged to:

decode a timing transmission from the source NB, the timing transmission comprising the time period of the autonomous handover timer.

3. The apparatus of claim 2, wherein:

the time period of the autonomous handover timer is dependent on mobility of the UE and channel occupancy of a channel used by the UE.

4. The apparatus of claim 3, wherein: the time period of the autonomous handover timer is inversely proportional to the mobility of the UE and proportional to the channel occupancy.

5. The apparatus of any one or more of claims 1-4, wherein the processing circuitry is further arranged to:

follow the handover command to perform network-controlled handover from the source NB to the target NB as the handover process when the handover command is received prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C- RNTI) of the target NB.

6. The apparatus of claim 5, wherein:

the network-controlled handover is a contention-free handover or random access channel (RACH)-less handover.

7. The apparatus of any one or more of claims 1-4, wherein:

the handover process is further dependent on whether autonomous handover information has been received from the source NB prior to expiration of the autonomous handover timer and prior to reception of the handover command, and

the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer.

8. The apparatus of claim 7, wherein the processing circuitry is further arranged to:

perform 2- or 4-step contention-based random access channel (RACH) handover procedure as the handover process from the source NB to a cell indicated by one of the target NB IDs when the autonomous handover information is received by the UE.

9. The apparatus of claim 7, wherein the processing circuitry is further arranged to:

perform, as the handover process, handover to a target NB based on the measurement report when the autonomous handover information is not received prior to expiration of the autonomous handover timer and prior to reception of the handover command.

10. The apparatus of claim 9, wherein:

the target NB is a neighbor cell that triggered the measurement report, and

the neighbor cell is a neighbor of the source NB.

11. The apparatus of claim 7, wherein:

the handover process comprises autonomous handover, the memory configured to store at least one of an event or autonomous handover criteria to trigger the autonomous handover.

12. The apparatus of claim 11, wherein the processing circuitry is further arranged to:

decode, from the source NB, a measurement event configuration that indicates at least one event to trigger the autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell.

13. The apparatus of claim 11, wherein the processing circuitry is further arranged to:

decode, from the source NB, cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell.

14. The apparatus of any one or more of claims 1-4, wherein:

the measurement report comprises a timestamp that indicates a time of initiation of the autonomous handover timer, and whether the handover command is received is dependent on the timestamp.

15. The apparatus of any one or more of claims 1-4, wherein:

carriers used in communication between the UE and the source NB are limited to the unlicensed band such that handover transmissions between the UE and the source NB occur on the unlicensed band.

16. The apparatus of any one or more of claims 1-7, wherein:

at least one of the source or target NB is an evolved NB (eNB).

17. The apparatus of any one or more of claims 1-7, wherein:

at least one of the source or target NB is gigabit NB (gNB).

18. The apparatus of any one or more of claims 1-7, wherein:

the processing circuitry comprises a baseband processor configured to encode transmissions to, and decode transmissions from, the source NB.

19. An apparatus of a source NodeB (NB), the apparatus comprising:

processing circuitry arranged to:

decode, from a user equipment (UE), a measurement report received on an unlicensed band in accordance with listen before talk (LBT), the measurement report comprising a timestamp that indicates a time of initiation by the UE of an autonomous handover timer;

determine from the measurement report, whether handover of the UE to a target NB is to occur; and

engage in a handover process of a plurality of handover processes in response to a determination that a handover of the UE to a target NB is to occur, the handover process on the unlicensed band in accordance with LBT, the handover process dependent on the autonomous handover timer; and

a memory to store the autonomous handover timer.

20. The apparatus of claim 19, wherein the processing circuitry is further arranged to:

encode, for transmission to the UE, a timing transmission, the timing transmission comprising the time period of the autonomous handover timer.

21. The apparatus of claim 20, wherein:

the time period of the autonomous handover timer is dependent on mobility of the UE and channel occupancy of a channel used by the UE.

22. The apparatus of any one or more of claims 19-21, wherein:

the handover is network-controlled contention-free or random access channel (RACH)-less handover when a handover command is transmitted from the source NB prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C- RNTI) of the target NB.

23. The apparatus of any one or more of claims 19-21, wherein the processing circuitry is further arranged to:

encode, for transmission to the UE, autonomous handover information after reception of the measurement report and prior to expiration of the autonomous handover timer and prior to transmission to the UE of a handover command, and

the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer.

24. The apparatus of claim 23, wherein:

handover to a target NB is based on the measurement report when the autonomous handover information is not received by the UE.

25. The apparatus of claim 23, wherein the processing circuitry is further arranged to:

encode, for transmission to the UE, at least one of:

a measurement event configuration that indicates at least one event to trigger autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell, or

cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell.

26. The apparatus of any one or more of claims 19-21, wherein the processing circuitry is further arranged to:

in response to a determination to handover the UE to the target NB, determine, based on the timestamp, whether the autonomous handover timer has expired;

in response to a determination that the autonomous handover timer has not expired, encode a handover command for transmission to the UE, the handover command configured to instruct the UE to handover to the target NB; and

in response to a determination that the autonomous handover timer has expired, avoid transmission of the handover command.

27. A computer-readable storage medium that stores instructions for execution by one or more processors of a user equipment (UE), the one or more processors to configure the UE to, when the instructions are executed:

initiate an autonomous handover timer based on triggering of a measurement report, a time period of the autonomous handover timer dependent on mobility of the UE and channel occupancy of an unlicensed spectrum channel used by the UE;

determine which of autonomous handover or network-based handover from a source NodeB (NB) to a target NB to perform dependent on whether a handover command and autonomous handover information have been received prior to expiration of the autonomous handover timer; and

perform the autonomous handover or network-based handover determined.

28. The medium of claim 27, wherein the instructions further configure the one or more processors to configure the UE to:

perform network-controlled handover when the handover command is received prior to expiration of the autonomous handover timer, the handover command comprising a Cell Radio Network Temporary Identifier (C-RNTI) of the target NB.

29. The medium of claim 27 or 28, wherein:

the autonomous handover information comprises a list of target NB identifiers (IDs) among which the UE is to select to handover when the handover command is not received prior to expiration of the autonomous handover timer; and when the handover command is not received prior to expiration of the autonomous handover timer, the instructions further configure the one or more processors to configure the UE to perform a 2- or 4-step contention-based random access channel (RACH) handover to a target NB indicated by one of the target NB IDs when the autonomous handover information is received by the UE and perform handover to the target NB based on the measurement report when the autonomous handover information fails to be received by the UE.

30. The medium of claim 29, wherein the instructions further configure the one or more processors to configure the UE to:

receive, from the source NB, a measurement event configuration that indicates at least one of:

at least one event to trigger autonomous handover, the at least one event comprising a measurement quality of at least one of the source NB or a neighbor cell, or

cell reselection criteria that comprises a ranking of the source NB and at least one neighbor cell.